Sanitation in Panama

by William Crawford Gorgas

The Board then went to work in earnest along lines which seemed calculated to develop the facts in the matter. They started a laboratory at Camp Columbia, the American military station a short distance out of Havana. Here they bred their mosquitoes from eggs procured from Dr. Finlay, and here the first three experimental cases occurred. The first case was severe; the second case was that of Dr. Carroll, a member of the Board, and was well marked, and Dr. Lazear, another member of the Board, died of the disease. Dr. Lazear visited Las Animas Hospital and was bitten by the mosquito on September 13, 1900; was taken sick September 18th and died September 25th. Previously on August 16th, he had been experimentally bitten by a mosquito which had ten days before bitten a yellow-fever patient in the fifth day of the disease. We know now that ten days is too short a time for incubation in the mosquito, and the fifth day a period too late for the yellow-fever patient to be infectious.

Dr. Carroll was intentionally bitten. Dr. Lazear told me after he was taken sick, and a day or two before he died, that he recalled being bitten by a stegomyia three or four days before he was taken sick, and while he was at work at Las Animas, our yellow-fever hospital in Havana. He said that he had noticed the mosquito enough to recognize that it was a stegomyia, and had allowed it to fill and fly away without disturbing it. These three cases satisfied the Board that the stegomyia mosquito was the means of conveying yellow fever, but they determined that they would make such a demonstration of the matter that there could be no doubt in the mind of any reasonable person as to what had been proved.

With this idea in view they selected a spot a mile or more from the military camp, which was well isolated and had no habitations near it. They agreed that if they established an experimental station here and kept their patients in such a way that there was no possibility of their getting out and contracting the disease elsewhere, then the results obtained in this station would be due to measures taken there. They already had their stegomyia mosquitoes which they had reared from the eggs procured from Dr. Finlay. These mosquitoes they took to the hospitals in Havana, and allowed them to bite people sick with yellow fever. In the course of time the Board found that the mosquito to become infected with this disease must bite the sick human being within the first three days of his disease. This was a singular and unexpected phenomenon, and is explained in this way. The mosquito injects the yellow-fever parasite into the blood of the human being; these parasites at once commence ejecting toxins into the blood in which they are circulating; these toxins irritate the human cells with which the poisoned blood comes in contact and they begin to throw into the blood circulation antitoxins. By the end of the third day these antitoxins have become so concentrated in the blood that they always kill the yellow-fever parasite, and after the third day no yellow-fever parasites remain in the human body.

Yellow fever is a very fatal disease, and on the average kills the patient on the sixth or seventh day. Why then does death occur in yellow fever if on the average the patient lives to the sixth or seventh day, and yet always by the end of the third day the yellow-fever parasites have been routed and destroyed in the great battle which has taken place between them and the body cells?

Dr. Reed established this fact by finding that mosquitoes which had bitten a patient more than three days after the patient had developed yellow fever, did not convey the disease to the non-immune when he attempted to infect these non-immunes with such mosquitoes. On the other hand, he found that he was almost always able to give these non-immunes yellow fever when he used mosquitoes which had bitten the man sick with yellow fever within the first three days of his symptoms.

We have followed Dr. Reed now up to the point of his having infected mosquitoes and being ready to transmit the disease to non-immune human beings. A human being, in order that he may be liable to yellow fever, must be non-immune, and by immune I mean a person who either has had yellow fever, or has lived ten or more years in a locality where yellow fever prevails. An attack of yellow fever gives a great immunity to the disease, probably just as much as occurs in the case of smallpox. In practice, it is counted as absolute. In over two thousand cases of yellow fever which I have treated personally or seen in consultation, I have never seen a single case with a second attack, in which I saw the same individual in the first attack. I have seen several, however, who believed that they had had a previous attack, and I myself believe that I saw them in their second attack. I have by no means seen a quarter as many cases of smallpox as I have of yellow fever, yet I have seen more cases of second attacks of smallpox than I have of yellow fever. I feel confident, therefore, in stating that yellow fever gives fully as great immunity as does smallpox.

It is well known that in a yellow-fever endemic center such as was Havana during the nineteenth century native Havanese are not liable to yellow fever. They look upon their immunity as being absolute, and in my experience of fourteen years of life in such endemic centers I am inclined to accept their belief. The immunity of the native is explained by saying that he has probably had yellow fever in childhood when the disease was very mild, and that, at the time, it was overlooked and not recognized. This is the best explanation that, so far as I know, can be made of the facts in the case.

Certain it is that one of these endemic centers from which yellow fever has been banished for a number of years may have yellow fever as badly as a city in which it has never been endemic. Eighty years ago a native of Mobile, Alabama, or Pensacola, Florida, looked upon himself as being as immune to yellow fever as did the Havanese twenty years ago. But at the present time the native of either of these cities is just as liable to yellow fever as is the man from New York. This is explained by the fact that eighty years ago they had yellow fever so frequently in Mobile and Pensacola that all the natives had this disease in childhood. Within the last fifty years they have had it so infrequently that very few now living in those cities have had this disease.

Another phase of the same condition is seen in Ecuador. Guayaquil, the port of Ecuador, is located on Guayas River at sea level, not more than three degrees from the equator. Here yellow fever always prevails, and the native of Guayaquil is not liable to the disease and never has it. Quito, the capital of Ecuador, is situated about two hundred miles away, right on the equator, and on the great Andean plateau ten thousand feet above sea level. The stegomyia cannot breed at Quito, so that yellow fever has never occurred there. The native of Quito, therefore, has no immunity to yellow fever, and of this he is well aware. Guayaquil is the only seaport of Ecuador, and everyone leaving the country has to leave through this port. Hundreds of the natives of Quito have died of yellow fever contracted by passing through Guayaquil. The man from Quito dreads Guayaquil a great deal more than did the American in the early days fear Panama.

Dr. Reed, therefore, to make his experiments of any value, had to get human beings who had neither suffered from yellow fever itself, nor had lived long enough in an endemic center to acquire immunity. Havana for a number of years had received a considerable Spanish immigration. At the time to which I refer, it amounted to about twenty thousand a year. These immigrants believed that they were going to have yellow fever, and though they knew that a considerable number of them must succumb during the process, they were anxious to have the disease and be done with it. There was a very general belief among the Spaniards in Havana that a person with what they called “thin blood” as contra-distinguished from a robust, plethoric, full-blooded person, was much more likely to recover from yellow fever. They tried, therefore, with their newly arrived friends, relatives and dependents from Spain to bring about this condition of their blood. They kept them confined in a darkened room and fed them on a very limited diet, and certainly succeeded in rapidly reducing the strong, florid, robust Gallego to a very marked condition of anemia and debility. The Spaniard believed that he thus saved many lives. I was convinced that he thus killed a good many of his friends and dependents.